1. Field of the Invention
The present invention relates to a pavement-vehicle convoy.
For applying cover layers of bituminous or concrete road-surface material, e.g. for applying two-layered cover layers, two or more units are combined so as to form a pavement-vehicle convoy. The smallest pavement-vehicle convoy comprises either two road-surface finisher units or one road-surface finisher unit and an associated charger unit. A mechanical coupling (U.S. Pat. No. 5,100,277) cannot be realized in the case of self-propelled units because, in practice, the respective travelling motions never correspond for geometrical, mechanical and other reasons. Hence, it has up to now been the task of the plurality of drivers to keep the mutual distances between the units constant as far as possible. In pavement-vehicle convoys used in practice the units travelling in convoy are controlled by a corresponding number of very experienced drivers from a respective operating cabin including an operation control device. A so-called travel master controller serves in each unit for switching on and off the drives of the travelling mechanism and all. road-surface applying units. Parameters (travelling speed, adjustment level of the road-surface applying screed, tamper speed and vibration) which have been adjusted prior to a stopover are reproduced automatically and precisely in each unit when the unit starts to move again. Automatic steering systems are used for controlling the direction, said automatic steering systems being adjusted to a reference line. These auxiliary devices make the driver's work easier, but they have not solved the problem of observing the respective distances.
When two-layered or multi-layered cover layers are applied, the distance between the respective road-surface finishers in the pavement vehicle convoy should be kept constant to a very large extent, since, if the distance changes, the temperature conditions for the respective subsequent layer applied will change and noticeably impair the final quality. If at least one charger is included in the pavement-vehicle convoy, it may, due to the presence of this charger, become even more difficult to observe the respective distances especially between the road- surface finishers.
2. Description of the Related Art
EP-A-0 667 415 discloses that, when a road-surface finisher is charged by a truck or a charger vehicle, distance and filling level measurement is used so as to automate the charging operation to a large extent.
Further prior art is contained in FR-A-2697547 (WO9410384A) and DE 9204559.